A: Ideas of order and harmony were promoted in Neoclassical art.
The Enlightenment spirit of the 18th century valued the order and harmony seen in Greek and Roman culture and sought to emulate it. As one art historian, writing The Art Post Blog, has stated, the idea spread that "Greek and Roman artistic perfection was the only form to imitate, in order to give an image of beauty and harmony."
As to the other answer options:
Enlightenment thinkers followed a variety of religious patterns, but not typically polytheism. Deism and rational religion were popular approaches to religion by "enlightened" persons, and some even chose atheism.
Enlightenment philosophers championed the ideas of humanism and individual rights.
The Baroque style of art did not disappear as soon as Neoclassicism appeared. Baroque styles continued throughout the 18th century and evolved also into the Rococo style.